# chull

0th

Percentile

##### Compute Convex Hull of a Set of Points

Computes the subset of points which lie on the convex hull of the set of points specified.

Keywords
graphs
##### Usage
chull(x, y = NULL)
##### Arguments
x, y

coordinate vectors of points. This can be specified as two vectors x and y, a 2-column matrix x, a list x with two components, etc, see xy.coords.

##### Details

xy.coords is used to interpret the specification of the points. Infinite, missing and NaN values are not allowed.

The algorithm is that given by Eddy (1977).

##### Value

An integer vector giving the indices of the unique points lying on the convex hull, in clockwise order. (The first will be returned for duplicate points.)

##### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988). The New S Language. Wadsworth & Brooks/Cole.

Eddy, W. F. (1977). A new convex hull algorithm for planar sets. ACM Transactions on Mathematical Software, 3, 398--403. 10.1145/355759.355766.

Eddy, W. F. (1977). Algorithm 523: CONVEX, A new convex hull algorithm for planar sets [Z]. ACM Transactions on Mathematical Software, 3, 411--412. 10.1145/355759.355768.

##### See Also

xy.coords, polygon

• chull
##### Examples
library(grDevices) # NOT RUN { X <- matrix(stats::rnorm(2000), ncol = 2) chull(X) # } # NOT RUN { # Example usage from graphics package plot(X, cex = 0.5) hpts <- chull(X) hpts <- c(hpts, hpts) lines(X[hpts, ]) # } 
Documentation reproduced from package grDevices, version 3.6.0, License: Part of R 3.6.0

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